LAGOS, Nigeria -- An elite Nigerian police squad set up to combat violent crime is torturing detainees to extract lucrative bribes and confessions, Amnesty International said in a report published Wednesday.

The report says the Special Anti-Robbery Squad demands bribes, steals and extorts money from criminal suspects and their families.

"A police unit created to protect the people has instead become a danger to society, torturing its victims with complete impunity while fomenting a toxic climate of fear and corruption," said Damian Ugwu, Nigeria researcher for the London-based human rights organization.

The Nigeria Police Force spokesman, Deputy Commissioner Donald Awunah, did not respond to requests by The Associated Press for comment. Amnesty International said its questions about why no officers have been prosecuted met with a police denial that any torture occurs.

The report says many officers bribe police chiefs to get onto the special squad where "torture is a lucrative business" and that "the police chiefs in charge are themselves entwined in the corruption."

Amnesty said it had received reports from lawyers, human rights activists and journalists and collected testimonies from victims to uncover "a pattern of ruthless human rights violations."

The U.S. State Department's report on human rights in Nigeria notes that an anti-torture bill passed by the legislature still awaits the signature of President Muhammadu Buhari. It says reports indicate that "security service personnel regularly tortured, beat, and abused demonstrators, criminal suspects, militants, detainees and convicted prisoners. Police repeatedly mistreated civilians to extort money" and confessions later used to convict suspects.

Buhari promised to stamp out endemic corruption when he won elections in March 2015, but it is proving an uphill battle in this West African nation where graft pollutes every sector of life.